Mighty Mule 500/502 repair

Hello, I have had some trouble with my mighty mule 500 opener arm. I found a place to buy the motor, switches and resistors for them, then the control board went bad. after fixing this one and some for friends, I have gotten pretty good at it! LOL Just wondering if anyone has replaced these and has the old ones around that I can rebuild for others needing them. Mighty mule wants near $300 for new and I can rebuild them and sell for about $125 if I can get cores. Will pay $20 for usable cores, or rebuild yours for you. maybe can help others not have to pay $300 for new one. 8303399652 Lester